Grinding and polishing glass



1 2,757,494 GIN G AND POLISHING GLASS Charles Edouard Chaudron, Tamines,Belgium No Drawing. Application June 4, 1952, Serial No. 291,809 Claimspriority, application Belgium June 12, 1951 18 Claims. (Cl. 5l--283) Theinvention relates to the grinding and polishing of glass, and isparticularly concerned with the tools used to this end.

According to the today usual practice the grinding and polishing ofglass is effected by means of tools called grinders moved in parallelrelation to the surface of the Work and between which and said surfaceis interposed an abrasive substance, usually sand of increasing finenessas the Work is progressing, the polishing operation being effected orcompleted by means of felts and the so called rouge as abrasive medium.The abrasive medium is fed to the tools and felts in the form of asuspension in a liquid, usually water.

This known method presents several drawbacks amongst which may be namedthe difficulties encountered for regularly and uniformly feeding theabrasive medium to the grinding and polishing tools, especially where acontinuous ribbon of flat glass is being ground or polished on bothfaces simultaneously, in which case the proper feeding in abrasive tothe bottom tools is especially difficult to obtain. The main object ofthe invention is to remedy these drawbacks.

To this end, the invention consists in no longer using the abrasivemedium in the form of a suspension in a liquid, but in the form of anagglomerate with an associated binder in order to obtain a coherent bodyto which may be imparted the shape of a body having definite sizes, forexample a disc, suitable as a tool for performing grinding and polishingoperations.

According to another feature of the invention, there are incorporated inthe agglomerate materials which by nature are comparatively soft and,preferably, in addition, may be easily impregnated with a binder toimpart to the agglomerate or shaped body some degree of resiliency and agood cohesion.

Such materials may be various kinds of fibres of animal, vegetal ormineral character, wood sawdust, paper or similar, substances.

As a binder, any material may be used which is adapted to perform thefunction of a binder. In accordance with a preferred embodiment,however, use is made of a natural or synthetic resin incorporated in aproportion as reduced as permissible to afford a suificient retainingaction on the abrasive grains under the operating conditions to whichthe tool is subjected at the stage of the process to which said tool isrelated.

When use is made 'of a resin such as a vinylic or similar resin, thebinder may be incorporated in a few number of per cent, for example 1 to7%, these limits being for example only.

However, it has been found in practice that disc shaped bodies so formedenable the grinding and polishing of the glass to be effected with toolsof moderate size and when use is made of moderate working pressures, butthat when the size of the tools is increased and particularly when useis made of working pressures of high values, increased proportions ofthe binder are to be incorporated in the mixture.

Working pressures of high values are of particular interest in that theypermit the duration of the operation to be materially reduced on the onehand, and on the other hand to obtain the necessary amount of abrasivesubstance for an accelerated grinding or polishing operation to bedelivered by the tool itself.

trite States Patent 6 "ice According to this feature of the inventiontherefore, comparatively high proportions of the binder are incorporatedin the mixture from which the grinding or polishing tools are made,these proportions increasing with the increase of the contemplatedworking pressure.

It has been found that satisfactory proportions are from 15 to 40% byweight of the mixture when the binder used is a vinylic resin and thefilling substance is saw dust, the tools being of disc shape having adiametre from 30 to cms. and with a working pressure comprised between 5and 15 kgs. per square decimetre. However these proportions may bevaried according to the binder and/ or the filling material used.

in present practice of the polishing of glass, use is made of so calledfelts and experience has shown that high grade felts only that areformed with long fibers are economically usable.

When in producing tools in accordance with the invention use is made offibrous material as filling component, low grade felts and even wasteproducts may be used and still obtaining very good results in thepolishing operation.

The following examples are illustrative of the invention.

Example 1 In the grinding-polishing of fiat glass on a test machine, onwhich the advance of the work was cms. per minute, with a linearvelocity (mean rotation speed) of the tool of 4 m. per second and with aworking pressure of 6 to 7 kgs. per square decimetre, the polishing waseffected with disc shaped tools having a diametre of 30 cms. and thefollowing compositions:

Percent (0) Sand (similar to the sand used at the end of the grindingoperation as usually effected) 65 to 55 Sawdust 12 Polyvinyl acetate a-15 to 25 (b) Rouge 60 to 50 Sawdust l5 Polyvinyl acetate 25 to 30 Afinish was obtained quite similar to that normally secured with 25 toolsas usually used (each including three rotating discs arranged around arotating shaft) and with an advance of the work of 300 cms. per minuteand a linear velocity of tool of 4 m. per second. In this test four sandtools (a) and 10 rouge tools (b) only were used.

Example 2 Under similar conditions as in Example 1, but with a workingpressure of about 8.5 kgs. per square decimetre for the sand tools and6.5 kgs. per square decimetre for the rouge tools, tools having thefollowing compositions were used:

Percent (0) Sand (similar to the sand used at the end of the grindingoperation as usually effected) 61 to 51 Sawdust Urea-formaldehyde(resin) 30 to 40 (d) Rouge 58 to 48 Sawdust 17 Urea-formaldehyde (resin)25 to 35 Results comparable to those of Example 1 were obtained.

Example 3 In each of the above cases no appreciable heating of 3 thework has been experienced with either of the sand or rouge tools.

I claim:

1. A method for grinding or polishing sheets of glass havingsubstantially the same thickness over the entire area of their broadsurfaces comprising rubbing the said broad surfaces of the sheets with abody of abrasive particles of substantially the same size agglomeratedin coherent formation by means of a binder, said binder in cluding aresin, applied to the work through a fiat face thereof and retainedunder dry working conditions substantially in permanent contact with thework through substantially the entire area of the said flat face.

2. A method as in claim 1 wherein the resin is a synthetic resin.

3. A method as in claim 1 wherein the resin is polyvinyl acetate.

4. A method for grinding or polishing sheets of glass havingsubstantially the same thickness over the entire area of their broadsurfaces comprising rubbing the said broad surfaces of the sheets with abody of abrasive particles and a filling material of soft nature individed form agglomerated in coherent formation by means of a binder,applied to the work through a flat face thereof and retained under dryworking conditions substantially in permanent contact with the workthrough substantially the entire area of the said flat face.

5. A method as in claim 4 wherein the filling material of soft nature individed form includes sawdust.

6. A method as in claim 4 wherein the filling material of soft nature individed form is a fibrous substance.

7. A method as in claim 4 wherein the filling material of soft nature individed form includes felt waste.

8. A method for grinding or polishing sheets of glass havingsubstantially the same thickness over the entire area of their broadsurfaces comprising pressing on and moving in parallel relation to sucha broad surface of the sheets a coherent body of abrasive particleshaving free side surfaces and therebetween a fiat Working surface of oneto four square feet and agglomerated by means of 15% to 40% by Weight ofsynthetic resin as a binder, said body being retained under dry workingconditions in substantially permanent contact with the work throughsubstantially the entire area of said flat working surface.

9. A method as in claim 8, wherein the agglomerated coherent body isapplied to the work with a pressure from 50 to 150 kg. per square foot.

10. A method as in claim 8, wherein the agglomerated coherent bodyincludes from 9 to 17% by weight of a soft material in divided form.

11. A method as in claim 8 wherein the agglomerated coherent bodyincludes from 50 to 60% by weight of abrasive particles of substantiallyuniform size.

12. A method as in claim 8, wherein the work is moved With a linearvelocity of about 75 cms. per minute, and the agglomerated coherent bodyis rotated with a mean rotation speed of about 4- m. per second.

13. A method for grinding or polishing sheets of glass havingsubstantially the same thickness over the entire area of their broadsurfaces comprising rubbing the said broad surfaces of the sheets with acoherent body of an agglomerate of abrasive medium and a binder, appliedto the work through a fiat face thereof and retained under dry workingconditions substantially in permanent contact with the work throughsubstantially the entire area of the said flat face.

14. A method for grinding or polishing sheets of glass havingsubstantially the same thickness over the entire area of their broadsurfaces comprising rubbing the said broad surfaces of the sheets with acoherent body of abrasive particles agglomerated by means of a binder,applied to the work through a fiat face thereof and re tained under dryworking conditions substantially in permanent contact with the workthrough substantially the entire area of the said fiat faces.

15. A method for grinding or polishing sheets of glass havingsubstantially the same thickness over the entire area of their broadsurfaces comprising rubbing the said broad surfaces of the sheets with abody of abrasive particles and a filling material in divided formagglomerated in a coherent formation by means of a binder, applied tothe work through a flat face thereof and retained under dry Workingconditions substantially in permanent contact with the Work throughsubstantially the entire area of the said flat faces.

16. A method for grinding or polishing sheets of glass havingsubstantially the same thickness over the entire area of their broadsurfaces comprising pressing on and moving in parallel relation to sucha broad surface of the sheets a coherent body of abrasive particlesagglomerated by means of a binder, having free side surfaces and fiatexternal surfaces therebetween and retained under dry working conditionsin substantially permanent contact with the work through substantiallythe entire area of a flat face thereof.

17. A method for grinding and polishing sheets of glass havingsubstantially the same thickness over the entire area of their broadsurfaces comprising pressing on and moving in parallel relation to sucha broad surface of the sheets a body of abrasive particles and a fillingmaterial of soft nature and divided form, retained in coherent formationby means of a binder, having free side surfaces and flat externalsurfaces therebetween and retained under dry working conditions insubstantially permanent contact with the Work through substantially theentire area of a flat face thereof.

18. A method for grinding or polishing sheets of glass havingsubstantially the same thickness over the entire area of their broadsurfaces comprising pressing on and working in parallel relation to sucha broad surface of the sheets a coherent body of abrasive particleshaving free side surfaces and therebetween a flat working surfacesmaller that one square foot and agglomerated by less than 7% ofsynthetic resin as a binder, said body being retained under dry Workingconditions in substantially permanent contact with the work throughsubstantially the entire area of said flat working surface.

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